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Scientists Uncover Pinta Tortoise Hybrids in the Galapagos Islands

November 15, 2012

A Pinta hybrid tortoise found on Wolf Volcano. Photo by Yale Univ.

Scientists have discovered several giant tortoises with partial Pinta Island ancestry on Isabela Island in the Galapagos Islands. The death of Lonesome George, the last known pure Pinta Island Giant Tortoise (Chelonoidis abingdoni), who passed away on June 24, 2012, may not have signaled the end of his species.

After years of cutting-edge genetic research on the giant tortoises of Galapagos, scientists from Yale University report finding 17 tortoises with some Pinta Island ancestry living in the wild on Wolf Volcano on Isabela Island. In an article published in the scientific journal Biological Conservation, lead author Dr. Danielle Edwards of Yale University recounts the discovery of multiple, unrelated individuals with partial Pinta ancestry, including five juveniles.

The view of Isabela Island from the top of Wolf Volcano. Photo by Mike Russello.

The tortoise genetics study, headed by Yale University’s Dr. Adalgisa (Gisella) Caccone, compared the DNA from museum specimens of Pinta tortoises and Lonesome George with more than 1,600 samples collected in 2008 on Wolf Volcano. The Yale group speculates that, given the ages of the 17 tortoises found and the huge number of unsampled tortoises on Wolf Volcano, there may still be additional hybrids and possibly even purebred Pinta tortoises. “This spectacular discovery is the first step toward the potential recovery of the Pinta Island Tortoise, a dream of mine since the early 1980s,” said Dr. Linda Cayot, Galapagos Conservancy’s Science Advisor.

Although separated by only 37 miles, it is unlikely that the ocean currents between Pinta and Isabela Islands could have carried tortoises from one to the other. However, Banks Bay on the northwestern coast of Isabela was used often by both naval and whaling vessels in the 1800s. The log of Captain Porter of the USS Essex records at least one instance of British whalers throwing giant tortoises, which were probably collected on several different islands, into the bay to escape pursuit. Given that the hybridization events on Wolf appear to have started approximately 200 years ago, the presence of the non-Wolf tortoises is most likely due to transfers by humans in the 1800s.

Given the ecological importance of giant tortoises to their island ecosystems, the incorporation of tortoises with Pinta genes into a captive breeding program is the preferred path toward the reestablishment of a reproductive population on Pinta. In addition to returning the island’s most important ecosystem engineer, this action will preserve the evolutionary legacy of Lonesome George’s species.

Scientists take blood samples from tortoises on Wolf Volcano. Photo by Joe Flanagan.

In 2013 and beyond, the Galapagos National Park and its many collaborators will conduct a series of expeditions to Wolf Volcano to sample more tortoises and bring Pinta hybrids into captivity to initiate a breeding program.

This extraordinary news would not have been possible without the tireless efforts of scientists, veterinarians, conservation managers, and Galapagos National Park rangers. The investments of Galapagos Conservancy and its donors provided funding at a critical time to move this project forward. GC donors also funded a Tortoise Workshop in Galapagos in July 2012, organized and facilitated by Dr. Cayot, to develop a multi-institutional 10-year research and management plan, including the work on Wolf Volcano. The Giant Tortoise Recovery Project aims to restore all extant tortoise populations and their islands, as well as reestablish reproductive populations of giant tortoises to Pinta, Floreana, and Santa Fe. Learn more about the Giant Tortoise Restoration Initiative and how you can support this important effort.